Modern Masonry: Fire Protection and Enhanced Performance

A proven material upgraded for code consistency, fire protection, and high-performance building

This course is part of the Masonry Academy

Fire safety is one of the paramount responsibilities of architects and developers, and it is dependent on careful selection of materials and proper design. Deficits in either area may result in a building fire, which can be a dramatic and devastating event, often incurring extensive property damage and, unfortunately, loss of human life.

Since February 2017, a number of high-profile fires have occurred in large wood structures in cities across the country, notably Oakland, California; St. Petersburg, Florida; Arlington, Virginia; College Park, Maryland; Overland Park, Kansas; Raleigh, North Carolina; and Maplewood, New Jersey. It is important to note that these were construction fires, not fires that occurred in a completed and occupied building.

The building type in question—wood-framed construction over a concrete podium—is a relatively new but highly popular design, enabled by the International Building Code’s increase in allowable height for wood construction in apartment buildings. The finished building, equipped with sprinkler systems and fire separations, is considered safe. But building codes may not fully address life safety and property protection during the construction period, and that is often when a building is most vulnerable to damage. Some maintain that structures built of wood are particularly vulnerable during construction for a number of reasons.

Wooden structures are considered “lightweight” combustible construction, a scenario that promotes specific fire risks. In addition, in the early construction phase, drywall may not yet be installed, sprinklers systems activated, or fire alarms, fire separation devices like gypsum board, fire doors, etc. in place. Further, wooden structures have void spaces between floors and ceilings where fire can spread quickly and undetected, whereas noncombustible materials slow the flame spread.

According to Jason Thompson, vice president of engineering for the National Concrete Masonry Association (NCMA), the evolution of building codes over the past 30 years from prescriptive to performance based counts heavily in the “beginning of the end of the inherent fire robustness of our buildings.” He explains that building codes now allow usage of fire-rated assemblies of combustible construction. “The inherent redundancy of a concrete block firewall has been lost,” he says. “If a fire starts, it can burn quickly through the building.” And the increase in allowable height of wood construction presents a double whammy. “A wood-framed apartment complex consisting of 500 units has a significantly greater fuel load, and due to its size, can inhibit firefighter access during a fire,” Thompson adds.

While the perception is that wood-framed midrise buildings offer cost-effective, high-density structures that can be constructed quickly with a low carbon footprint, some firefighting groups as well as cities and towns have expressed concern over their safety and are pressing for a ban on the use of combustible materials in multifamily construction. “A hard look is being taken at whether the pendulum has swung too far in permitting larger wood-framed buildings,” Thompson says. “It’s happening nationally, regionally, and at the state and municipal level with varying levels of traction and implementation.” Examples include the town of Sandy Springs, Georgia, which passed an ordinance disallowing this type of construction, and the states of New Jersey and Maryland, where similar legislation is under review.

While no building material is totally immune to fire, alternative noncombustible materials can be an effective option. Masonry is one such material that carries minimal risk of fire during construction or otherwise. It has been used for thousands of years, demonstrating nearly unparalleled durability and the ability to withstand adverse natural and manmade events. But rather than being an “antiquated” medium, however, masonry is a proven solution well suited for modern codes and design, with today’s masonry products combining the material’s inherent attributes and upgrade options that are enhancing the natural qualities of block with insulation, moisture control, and strength. “Architects are being hand tied by building owners to use wood because of the cost savings,” says John Cicciarelli, national sales manager for Echelon Masonry. “The owner wants to save money, meet code, and get the building open. But that may come with a heavy price. As a proven noncombustible building material, masonry is a sound design solution that offers architects protection not only for their projects but for their business and personal reputation as well.”

This course will describe masonry’s inherent characteristics and how the material has been improved in order to withstand the threat of damage from fire, moisture, and mold, meeting today’s stringent code requirements and performance standards. Also discussed will be masonry’s architectural options to meet pleasing contemporary design standards.

Masonry and Fire Resistance

Masonry is a noncombustible material that does not fuel a fire or emit toxic gases. It is widely known for its fire resistance and commonly specified for fire walls and barriers. After severe fire exposure, concrete masonry can frequently be repaired by patching cracks and repointing mortar joints. “When exposed to fire, there is generally no damage to masonry construction. It will heat up and then cool down,” Thompson says. “Masonry is the quintessential noncombustible material. After all, we’re not building fireplaces and chimneys out of wood.”

Wood, on the other hand, is a combustible material. Thompson explains that wood construction is transitioning from traditional 2-by-4s to engineered lumber, which is composed of chips and sawdust to create a composite material offering greater strength with reduced weight, thus allowing larger spans, such as floors with engineeredwood joists. The problem from a fire standpoint is that engineered wood can burn more quickly due to the presence of resins and glues that bind the engineered wood members together, which can accelerate the fire spread. Another development in the wood industry is cross laminated timber (CLT), in which smaller pieces of timber are glued or nailed together to simulate heavy timber. Heavy timber will char, which does provide insulation from a fire, and will slow fire spread, although in time it will still burn. According to Thompson, the jury is still out on whether CLT acts like heavy timber in a fire, with third-party tests scheduled for later in 2017.

To prevent fire damage in multifamily housing, the concept of balanced design is particularly important. Balanced design is predicated on four strategies that work in unison.

• Prevention: Housekeeping, education, and building layout that decrease the likelihood of a fire starting in the first place.
• Detection and alarm: Smoke detectors and alarms to alert building inhabitants to a fire before it can spread.
• Suppression: Sprinklers, fire extinguishers, etc. to put out the fire quickly.
• Strategic compartmentation: Fire safety demands that a wall stop the spread of fire throughout the building and that it retain structural integrity throughout the fire-fighting operations. Building construction with masonry fire walls isolates and contains the fire and smoke while maintaining the building’s structural integrity—essential to safe evacuation and provision of safe areas to enable firefighters to work effectively. Masonry walls contain the fire and noxious gases and remain structurally stable.

It’s well-known fire-resistant qualities have made masonry a frequent building material of choice in fire stations. While there are no actual statistics on the subject, a large number of U.S. firehouses are built of masonry, not only for its fire-resistant properties but also for its aesthetic adaptability.

According to Bill Howell, architect and president of The Howell Group Inc. in Marietta, Georgia, who has designed 29 Georgia fire stations over the past 30 years, “Fire stations pose a unique opportunity for architects because towns need to add fire services as residential development expands to keep response time and insurance premiums both low.” They also pose a unique problem as they house people alongside highly combustible fuel in large trucks.

“I can’t think of any other situation in which to meet code, you are dealing with this type of mixed-use occupancy,” Howell says. “The International Building Code has specific separation requirements for the apparatus bay, or storage areas, and for the residential area. To meet code, you must separate the two types of occupancies with a fire-rated wall assembly, such as concrete block and/or sprinklers.”

The truck storage areas are viewed as hazardous, as the trucks store diesel fuel, so the building code requires a material with a 2-hour fire rating between the storage and residential areas if the building is without sprinklers. Howell achieves this with an 8-inch concrete block wall.

Because many fire stations are located in the residential areas they serve, aesthetics are important, and an unsightly industrial-looking fire station might decrease property values. Whether designing for a subdivision or a historic downtown, fire stations should blend seamlessly with the surroundings. Fire stations in historic areas do well with a dual stone exterior. One choice Howell made for a small Georgia town was to use conventional modular brick with masonry veneers with a hand-chiseled texture of natural stone around the base of the station and on the entrance columns. “We often use a cast stone on fire stations because the current trend for homes is toward a dual stone and brick exterior. It’s a nice, attractive look,” Howell says. “The client benefits from this as well because it is low maintenance, durable, and cost effective.”

Masonry and Moisture Resistance

One of the most significant concerns in designing a wall is moisture. Because concrete masonry is impermeable to infiltration by air or wind-driven rain, any moisture that enters a building must pass through the joints between elements. Any moisture that enters through the joints will not damage the concrete itself, which will dry if not covered by impermeable treatments.

Masonry approaches minimizing moisture penetration by providing redundancy in a four-level line of defense, including surface protection, internal protection, and drainage and drying, the idea being that water tightness of the wall will still be maintained even if one of these systems fails. This is referred to as the belt and suspenders approach. According to NCMA, successful moisture mitigation in concrete masonry walls involves a variety of techniques, including flashing and counter flashing, weeps, vents, water repellents, sealants, post-applied surface treatments, vapor retarders, and crack control measures, with all components considered for redundant use, yet with the appreciation that not all techniques will be suitable for all wall systems.

Sealing after completion is considered the 110-percent solution for keeping moisture out. A clear, solvent-based silicone elastomer can weatherproof custom masonry units, fill pores to prevent water infiltration, provide UV stability and graffiti protection, as well as control surface stains, efflorescence, and mildew. It also allows the surface to “breathe,” which is critical to allow the masonry to dry, should water breach the surface.

Masonry and Durability

Concrete has been in use for centuries, and one has only to consider its use by the Egyptians and Romans in structures that are still in use to gauge its durability as a construction material and its ability to maintain its design properties while resisting environmental effects. Structurally sound, able to withstand wind and gravity loads, and resistant to mold, insects, and vermin, and UV exposure, concrete masonry has also shown effectiveness in exposure to extreme environments, including coastal regions. With constant advances in ingredients, placing, and curing methods, concrete masonry will continue to be identified with longevity and low life-cycle cost.

Masonry Options For Today's Buildings

Manufactures are continually upgrading concrete masonry products to enhance value and performance beyond the inherent properties of standard block. A systems approach that incorporates several elements is fast becoming a new construction industry standard, as these products offer substantial efficiencies as well as installation and cost saving advantages. With these systems, a single pass installation simplifies the process, eliminating the need for added insulation, and already includes moisture management and finishing materials, thereby saving on labor costs.

Three such innovative systems that enhance the inherent qualities of masonry will be discussed below.

Masonry Foam Panel Systems

High-performance foam panel wall systems are a relative newcomer to the industry. These systems consist of polystyrene foam panels, stainless steel screws, or specially designed stainless steel anchors that affix the masonry solidly to the wood, steel, or concrete masonry structure of a building. In foam panel systems, engineered drainage channels on both sides of the foam evacuate any water that may infiltrate the wall, protecting the structure from damages over a lifetime of moisture exposure.

The key factor in system performance here is the foam, which gives a significant boost to R-values of walls and roofs with minimal increases in thickness. Foam panels can provide high R-values, 9.2 steady state, and include continuous insulation (CI). They also afford acoustical comfort with an STC rating of 61 on steel stud framing and have been proven to resist wind speeds up to 130 MPH (depending on building parameters) according to ASTM E330 with no lasting deformation, virtually eliminating the risk of structural damage. Compliance with NFPA 285 and ASTM E119 assures that tested foam walls have successfully withstood 1 hour of exposure to 1,700 degrees Fahrenheit and above. Foam panel systems may be used over any exterior fire-resistance-rated assembly without changing the assigned hourly rating up to 2 hours. Some systems may also be installed in seismic zones A to D and can be installed on metal-frame or wood-frame buildings up to climate zone 6, and on some buildings with proper installation detailing in zones 7 and 8.

In terms of installation, masonry units insert easily into the designed cells of the foam panels. Typically they are friction fit in the foam, with different types of units having different foam panels. Press fit is only temporary until the mason finally points the mortar at the joints of the veneers. The veneers will be mechanically linked to the base wall through the anchors that are embedded in the mortar as per typical anchored masonry installation. A variety of masonry units are available including durable stone, clay, and concrete brick, with others under development.

To recap, these foam systems are not traditional masonry units. They are insulated panel systems anchored to the exterior of a building substructure. The insulated panels have drainage planes built into both the front and rear as well as molded pockets or profiles that allow the veneer units to be held in place while the joints are mortared and struck. The foam panel systems combine enhanced performance capabilities with the aesthetics of traditional masonry.

Insulated Concrete Masonry Systems (ICMS)

Another enhanced option is the insulated concrete masonry system, or ICMS, which consists of a preassembled structural masonry unit, an insulation insert, a thin veneer face, and all components necessary to address inside and outside corners, windows, and door openings, maintaining a fully thermally broken envelope. The most effective of these assemblies include high-performance expanded polystyrene (EPS) molded insulation inserts that give the assembled unit a total effective R-value of 16.2 at 75 degrees Fahrenheit.

The engineered EPS inserts are designed with a vertical shiplap, and the system also includes a closed-cell foam gasket installed on the horizontal joint to ensure a continuous insulation without air leakage.

The ICMS meets IECC Energy code requirements from zones 1 through 7.

Stainless steel metal anchors molded into the EPS confer superior structural stability through a safety connection to the back wall during windloading as well as for fire safety. With the veneer and anchors, the wall system can withstand up to 100 PSF of windload. Some ICMS include two additional drainage planes at each side of the continuous insulation for more effective moisture management—particularly useful as buildings age and water infiltrates cracks in the mortar. These drainage planes eliminate the likelihood of mold and mildew.

The ICMS is particularly useful in a regulatory environment of increased R-values. These insulated systems are also fairly adaptable in size, shape and density, which eliminates the need to glue together multiple boards to achieve the desired insulation thickness. This approach is valuable to architects seeking R-value targets in thickness-constrained applications. As R-value targets continue to increase, these insulated systems are a prime opportunity to easily adapt as a slight increase in insulation thickness can provide the necessary thermal performance.

Mortar Admixture: Upping Masonry’s Moisture Control

Another way in which traditional masonry material has been upgraded is through water-repellent admixtures, which have proven to be effective in controlling moisture intrusion. The “secret sauce” here is the anti-wicking action of the integral water repellent, which acts to minimize water absorption and permit any water that has breached the surface to drain toward flashing and weep holes. Untreated masonry, on the other hand, will usually absorb water through capillary suction or wicking. The admixture is not entirely impervious to moisture, however, which makes the masonry “breathable.”

Three types of admixture have been used in the past: calcium stearate, tall oils, and polymetric. Of the three, the polymetric creates a surer bond between mortar and masonry units. The air component of the admixture will vary by brand, and the higher the air content, the lower the compressive strength, which can jeopardize the bond. On the other hand, insufficient air content will decrease the mortar’s freeze-thaw resistance. In addition to having adequate air content, polymeric admixtures make for a denser, more uniform unit that controls moisture and carries a minimal risk of efflorescence.

Admixtures are particularly effective in lightweight concrete masonry units and single wythe construction in protecting against water infiltration and wind-driven rain. Because joints are especially susceptible to moisture infiltration, specification of both masonry units and mortar with an integral water repellent is recommended to achieve the fullest moisture protection. Recently developed specially engineered granulated formulas can be added to the mortar/sand during the blending process of premixed mortars to improve bond strength over the service life of the building.

Integral water-repellent mortars are available in liquid and powder form. Powders are typically found in preblended mortars. Each type of mortar is available in Type M, S, and N compressive strengths in compliance with ASTM C270 and is engineered as a preblended mortar for consistency, workability, and yield, providing consistent factory controlled mixes, batch to batch, compared to field mixed mortars.

When selecting a water repellent, it is important to understand the difference between intregal repellents and those that are site applied. Integrated water repellents were designed to address the problems common with job site applied repellents. An integral admixture assumes accurate blending at the manufacturing facility and that it will be precisely metered, properly proportioned, subject to quality control measures, and delivered as specified. Its presence is detectable and can be verified after the mortar hardens. In job site applications, achieving consistency can be difficult, particularly in inclement weather. The surface life of site-applied water repellents ranges from two to seven years, with a two-coat system often recommended, which adds to the project schedule and budget. Before sealing can be finalized, untreated units may become wet, with ensuing potential moisture problems. Integral water repellents eliminate many of these concerns and require no measuring, mixing, or additional steps, minimizing job site mistakes and the need to stock and dispose of liquid admixture supplies.

Further, integral repellents are engineered as a preblended mortar for consistency, workability, and yield, and are formulated for extended board life, reducing the need to retemper in hot or windy climates. Special applications of these repellents are available for high-moisture environments, coastal climates, or where cement based mortar is the preferred material.

Based on C1384 testing by the National Concrete Masonry Association, essential to demonstrate water repellency standards for mortars, the most advanced preblended mortar products have demonstrated up to an 8 percent increase in flexural strength, significantly decreased resistance to water absorption, and a nearly 50 percent longer board life than untreated mortars.

For aesthetic purposes, color mortar is available and typically sold as masonry cement-based or portland/lime-based products in more than 36 standard colors and custom options. Some manufacturers have their own array of colored blocks sold in a kit format—these can be used in conjunction with water repellent masonry units to provide joint warranty wall system approaches to water repellency. It is important to note whether these products meet, or preferably exceed, ASTM C-270 and ASTM C-1384.

Masonry: An Important Place in Contemporary Building Design

Recently, there has been a rash of construction fires in wood-framed multifamily housing, which has caused some cities and states to reexamine the advisability of permitting larger wood-framed structures. Masonry, an ancient building material that has endured for centuries, is an attractive alternative to wood. Because masonry is noncombustible with widely recognized fire-resistant properties, it is typically specified in fire walls and barriers, and has a strong track record of safety in buildings during occupancy and throughout the construction phase as well. Today, some of the most successful new masonry products are systems that incorporate masonry’s inherent strengths while increasing building performance in a number of parameters, from fire resistance and moisture control to energy efficiency and sound attenuation. With a variety of aesthetic options and proven performance, today’s masonry systems have an important place in contemporary building design.

Echelon is the consolidated brand for all masonry products and services of Oldcastle Architectural including Trenwyth® Architectural Masonry, Artisan Masonry Stone Veneers®, Quik-Brik® Concrete Masonry Units, Amerimix® Bagged Goods and a complete portfolio of Performance Upgrades. As a single source masonry portfolio solution, Echelon delivers consistent, reliable product manufactured locally at more than 170 locations and delivered by an unrivaled logistics network. For more information, call (844) 495-8211 or visit EchelonMasonry.com